Lithium secondary battery containing organic electrolyte, active material for cathode thereof, and method for manufacturing the active material

Abstract

PCT No. PCT/JP94/00852 Sec. 371 Date Jun. 9, 1995 Sec. 102(e) Date Jun. 9, 1995 PCT Filed May 30, 1994 PCT Pub. No. WO94/28591 PCT Pub. Date Dec. 8, 1994The lithium secondary battery uses lithium or a compound containing lithium as an anode active material, and lithium nickel oxide as a cathode active material. This battery is produced to enhance the charge and discharge capacity. The lithium nickel oxide is prepared as follows. Nickel oxide which contains nickel of more than trivalence or a nickel salt which produces nickel of more than trivalence when heated, and lithium salt are mixed at an Li/Ni (molar salt ratio) of 1.0 to 1.5. After preheating the mixture, it is baked at a temperature of 680 DEG C. to 780 DEG C. in an oxygen atmosphere, thus producing a lithium nickel oxide. The primary differential absorption spectrum of the electron spin resonance of the lithium nickel oxide is a singlet (single line) when measured by use of an X band at a temperature of 77 K., and the line distance ( DELTA Hpp) between the peaks is 140 mT or more. The intensity ratio of the main peak of the components other than the lithium nickel oxide and that of the lithium nickel oxide in a powder X-ray diffraction image is lower than 0.03. The Li/Ni ratio (atomic ratio) is above 0.9, and the grain size of the primary particles is below 1 mu m.

What is claimed is: 
     
       1. A lithium secondary battery, which comprises: a cathode comprising a lithium nickel oxide as an active material, an anode comprising lithium or a compound containing lithium and an organic electrolyte, wherein the cathode active material is a lithium nickel oxide having a primary differential absorption spectrum of electron spin resonance measured at a temperature of 77 K. by using X band that is a singlet, and an intensity ratio of a main peak other than lithium nickel oxide and a main peak of lithium nickel oxide in a powder X-ray diffraction image (CuKα ray) that is 0.03 or less.   
     
     
       2. The lithium secondary battery containing organic electrolyte according to claim 1, wherein the lithium nickel oxide has an electronic structure which indicates the line width (ΔHpp) between the peaks of the primary differential absorption spectrum of the electron spin resonance measured at a temperature of 77 K. by using X band is 140 mT or more. 
     
     
       3. A lithium secondary battery containing organic electrolyte according to claims 1 or 2, wherein Li/Ni ratio (atomic ratio) of the said lithium nickel oxide is 0.9 or more and the average grain size of the primary particles is 1 μm or less. 
     
     
       4. A cathode active material for a lithium secondary battery containing an organic electrolyte, mainly composed of a lithium nickel oxide having a primary differential absorption spectrum of electron spin resonance measured at a temperature of 77 K. by using X band that is a singlet, and an intensity ratio of a main peak other than lithium nickel oxide and a main peak of lithium nickel oxide in a powder X-ray diffraction image (CuKα ray) that is 0.03 or less. 
     
     
       5. A cathode active material for the lithium secondary battery containing an organic electrolyte according to claim 4, wherein the lithium nickel oxide has an electronic structure which indicates the line width (ΔHpp) between the peaks of the primary differential absorption spectrum of the electron spin resonance measured at a temperature of 77 K. by using X band is 140 mT or more. 
     
     
       6. A cathode active material for the lithium secondary battery containing an organic electrolyte according to claim 4 or 5, wherein said lithium nickel oxide possesses a Li/Ni ratio (atomic ratio) of 0.9 or more, and wherein an average grain size of the primary particles thereof is 1 μm or less. 
     
     
       7. A method of synthesizing the lithium nickel oxide of the cathode in the lithium secondary battery according to claim 1, 2 or 3, which comprises the steps of: mixing a nickel oxide containing nickel with a valence of 3 or more, or a nickel salt producing nickel with a valence of 3 or more by heating, and a lithium salt, at a ratio of Li/Ni (molar salt ratio) of 1.0 to 1.5,   and heating the mixture at a temperature of 680° to 780° C.   
     
     
       8. A method of synthesizing the lithium nickel oxide of the cathode in the lithium secondary battery according to claim 7, wherein the nickel oxide containing nickel with valence of 3 or more is Ni 2  O 3 . 
     
     
       9. A method of synthesizing the lithium nickel oxide of the cathode in the lithium secondary battery according to claim 8, wherein the heating takes place in an atmosphere that is an oxygen stream or under an oxygen pressure. 
     
     
       10. A method of synthesizing the lithium nickel oxide according to claim 3 used for a lithium secondary battery containing an organic electrolyte which comprises steps of: mixing nickel oxide containing nickel with valence of 3 or more or nickel salt producing nickel with valence of 3 or more by heating, and lithium salt, at a ratio of Li/Ni (molar salt ratio)=1.0 to 1.5, and heating the mixture at a temperature of 680° to 780° C.